Patent GB-919616-A (GB)
Title: Improvements in or relating to the supply of control fluid to hydraulic clutches or brakes
IPC: F16D67/00
Filed: 1959-07-31
Abstract: 919,616. Variable-speed gear. REGIE NATIONALE DES USINES RENAULT. July 31, 1959 [Aug. 12, 1958], No. 26392/59. Class 80 (2). [Also in Group XXXIV] To control the rate of engagement of a ratio establishing clutch or brake in a variable-speed gear, one of the clutch or brake elements is adapted to permit a small angular movement relative to an associated part, this movement causing the cylinder of an oil-pressure servomotor engaging the clutch &c. to be connected with one or other of two ducts supplying oil under pressure according as the element is turned angularly in one direction or the other. In one form, a brake band 17, Fig. 2, is applied to station a reaction sun gear in a three-ratio planetary gear for a motor vehicle, and establish the second ratio. When a ratio selector valve 8 is moved to the second ratio position shown, an engine driven pump 1 supplying oil under pressure through a pipe 2 to an accumulator 3 and a pressure relief valve 4 is connected to two pipes 15, 16 energizing a servomotor space 20 for application of the brake band 17. A spring 19 biases two pistons 18, 18<SP>1</SP> within the servo space 20 to the position shown, where the piston 18 engages a holding circlip 26. The piston 18<SP>1</SP> now closes a port 40 at the end of the pipe 15, so that oil under pressure supplied thereto through the selector valve 8 is ineffective. The oil under pressure supplied to the pipe 16 first enters a valve servo 25 and moves its valve 22 downwards to close an exhaust passage 24. Oil in the pipe 16 also passes through a space 29 at the back of a ball-valve 30, opened against spring bias by a projection 33 on the base of the piston of an hydraulic accumulator 36. Oil in the space 29 passes through an orifice 37 to a pipe 38 leading to the accumulator 36, which begins to fill, the pipe 38 also leading to a port 39 now open to the servomotor space 20. A cushioned engagement of the brake band 17 is now initiated by the slow bleed of oil through the orifice 37 and the gradual filling of the accumulator 36. If the ratio selecting valve 8 is moved to the position shown from the first ratio position, and the torque of the engine driving the vehicle is maintained, the reaction element to which the brake band 17 is applied rotates in the opposite direction to the direction of rotation of the engine, which latter is shown by the arrow 43. Accordingly, as soon as the brake band 17 begins to bite, it is rotated clockwise against the bias of the spring 19, the piston 18 closes the port 39 and the piston 18<SP>1</SP> opens the port 40. Oil is then supplied rapidly through the pipe 15 to complete engagement of the brake and establish the second ratio in the gearing. If, however, the ratio selecting valve 8 is moved from the first to the second ratio position while engine torque is not maintained, the reaction element to which the band brake 17 is applied is rotating in the opposite direction, that is, in the direction of the arrow 43. Therefore, in this case, the port 40 remains closed, and completion of engagement of the brake band 17 is effected gradually as oil bleeds through the orifice 37 and fills the accumulator 36. If an upshift from second to third is effected while engine torque is maintained, the reaction on the band brake 17 holds the pistons 18, 18<SP>1</SP> downwards so that the port 39 is closed and the port 40 is opened. Pressure is maintained in the pipe 15, but the pipe 16 is vented to exhaust, so that the oil pressure in the space 25 falls, the valve 22 opens the pipe 23 to the exhaust 24, the pressure in the accumulator 36 also falls, but the brake 17 is maintained engaged by the pressure supplied to the port 40 through the pipe 15 until a direct drive friction clutch is engaged, when the reaction on the brake band 17 is reversed and the pistons 18, 18<SP>1</SP> move to the position shown. The servomotor space 20 is then vented to the pipes 23, 24. On moving the ratio selector valve 8 from the third to the second ratio position, while maintaining engine torque, the pipe 16 &c. is again opened to the pressure of oil, as before, but the reaction element to which the brake band 17 is applied now rotates in the direction of the engine, as shown by the arrow 43. Accordingly, the pistons 18, 18<SP>1</SP> are maintained in the position shown and pressure within the servomotor space 20 increases gradually due to the orifice 37 and the hydraulic accumulator 36. As the speed of the engine accelerates, the reaction element to which the band 17 is applied ultimately and momentarily becomes stationary, and then tends to rotate in the opposite direction. As soon as this occurs, the pistons 18, 18<SP>1</SP> are moved downwards against the bias of the spring 19, the port 39 is closed and the port 40 is opened for rapid establishment of the second ratio. As a modification, the two pistons 18, 18<SP>1</SP> may be replaced by a piston and a sleeve slidably mounted one in the other, the sleeve itself sliding in the cylinder 20 of the brake-applying servomotor and having on its periphery ports which register either with the port 39 or with the port 40. In a further modification, the control system of Fig. 2 is described applied to a multiple disc brake, Fig. 3, 4, comprising a ring 47 having peripheral teeth engaging within larger apertures 48 betweenteeth 52 formed in a non-rotary gear case 53, the arrangement being such that the ring 47 has a limited relative angular rotation with respect to the gear case. Two ports 39, 40, Fig. 4, corresponding to the same ports in Fig. 2, connect alternatively with a ring-shaped cylinder 44 containing a piston 45 biased by the application of oil pressure to engage the multiple brake discs. In the position shown in Fig. 4, the port 39 communicates with the ring-shaped cylinder 44, and the port 40 is closed. If, however, the brake member 47 is moved angularly in the direction of rotation of the car engine, that is, in a direction opposite to that shown by the arrow 55, the port 40 is opened and the port 39 is closed. Gearing.-The device is described applied to a three-ratio planetary gear in which the turbine C, Fig. 1, of a fluid coupling drives through a shaft D to a sun gear F meshing long planet pinions I intermeshing with larger diameter planet pinions J in turn meshing a reaction sun gear K stationed by a band brake N controlled by servo means according to the invention. The planet pinions I, J are mounted in a carrier fast with an output shaft G, the planet pinions I also meshing a ring gear P which can be stationed by a band brake Q. First ratio is obtained by applying the brake Q, second ratio by applying the brake N, and direct drive by engaging a multiple disc clutch E between the sun gear F and the reaction sun gear K.